Integrated Services Digital Network (ISDN) is an international communications standard that makes it possible to deliver multiple services in addition to the normal telephone (voice) service. With it, fax, video, data and all kinds of images can be transmitted to a terminal over a single line. The ISDN is provided by public network operators at both national and international levels. These carriers offer a choice of basic or primary rate access to the ISDN network. The basic access (also called 2B+D) provides two, 64 Kbps B channels for voice or data communications, plus one D channel for the controlling and the monitoring of the transmission, giving an aggregate speed of 144 Kbps. The primary rate (which is called 30B+D) offers up to 30 simultaneous, 64 Kbps B channels and one 64 Kbps D channel for an aggregate speed of 2 Mbps.
The performance offered by ISDN networks, and particularly the speed provided by the primary rate, has allowed the possibility of effective national and international communications between host computers, either IBM or non-IBM, running X25, SNA, TCP/IP or OSI applications, and a wide range of terminal equipments and users. Thus, a wide range of users, who are generally not specialists in the telecommunication field and in the structure and operation of the sophisticated telecommunication equipment involved, benefit from the high transmission rates and possibilities of the ISDN equipment.
For instance, the possibilities offered by the ISDN networks have allowed the creation and the development of electronic catalogs and multimedia databases. Electronic images which are stored on a central database can thus be accessed in a few seconds by multiple users within a country or across borders. Electronic and up-to-date catalogs allow travel agents, for example, to show specific resorts and hotels with much more detail than obtained by merely using a printed catalog. The tour operators can also benefit from these possibilities since the update of one single central database appears easier and cheaper. Also distributors and retailers can demonstrate products clearly, whether the items are cars, fashion or technical products, and let users browse through catalogs and place orders directly. Retailers can show a wide variety of models electronically without having to keep the whole expensive range on hand, and additions and deletions are easily handled. The ISDN network allows a set of up to 30 users to be connected simultaneously to one electronic catalog.
Furthermore, the possibilities which are offered by the ISDN networks also allow the development of file transfers where software can be downloaded or retrieved from a central host by remote branch office or distribution centers to take advantage of lower tariffs during non-peak hours.
As a conclusion, a wide number of different telecommunication users are allowed to benefit from the possibilities which are offered by the ISDN primary communications, including data, voice, and image transfers by means of a corresponding wide number of telecommunication applications.
Generally speaking, operators are aware of the numerous possibilities which are provided by use of the personal computers or workstations. Since workstations are becoming more and more "user-friendly", and include keyboard, mouse, icons and prompt messages displayed on the screen, the operator is accustomed to controlling a highly sophisticated computer. However, workstations, as such, are not adapted to the telecommunication field and particularly the ISDN primary communications which involve serious constraints.
As mentioned above, since the use of ISDN telecommunication primary services are likely to be used by a wide range of operators having different skills (such as in travel agency, real estate agency, retailing and distribution applications), a need has appeared to have an ISDN primary gateway based on a "user-friendly" workstation so that any operator, regardless of his personal skill and experience in the telecommunication field, can be provided with a simple and efficient apparatus allowing customization, configuration, line connection, error and directory management and data traffic control.
Workstations based on personal computers have achieved wide acceptance because they provide the user with high data processing resources while ensuring ease of use.